1. Field of the Invention
The present invention relates to the drilling and completion of well bores in the field of oil and gas recovery. More particularly, this invention relates to an apparatus to provide selective communication of control fluid through a downhole tool, such as a safety valve. A method of using the communication tool apparatus is also described.
2. Description of the Related Art
In the oil and gas industry, a production tubing string is typically run thousands of feet into a well bore. Generally, when running a tubing string downhole, it is desirable—and in some cases required—to include a safety valve on the tubing string. The safety valve typically has a fail safe design whereby the valve will automatically close to prevent production from flowing through the tubing, should, for example, the surface production equipment be damaged or malfunction.
Should the safety valve become inoperable, the safety valve may be retrieved to surface by removing the tubing string, as described hereinafter. The tubing retrievable subsurface safety valve (“TRSSSV”) may be a flapper-type safety valve, a ball-seat type of valve, or other types of valves known in the art. The TRSSSV is attachable to production tubing string and generally comprises a flapper pivotally mountable on the lower end of the safety valve assembly by a flapper pin, for example. A torsion spring is typically provided to bias the flapper in the closed position to prevent fluid flow through the tubing string. When fully closed the flapper seals off the inner diameter of the safety valve assembly preventing fluid flow therethrough.
A flow tube is typically provided above the flapper to open and close the flapper. The flow tube is adapted to be movable axially within the safety valve assembly. When the flapper is closed, the flow tube is in its uppermost position; when the flow tube is in its lowermost position, the lower end of the flow tube operates to extend through and pivotally open the flapper. When the flow tube is in its lowermost position and the flapper is open, fluid communication through the safety valve assembly is allowed.
A rod piston contacts the flow tube to move the flow tube. The rod piston is typically located in a hydraulic piston chamber within the TRSSSV. The upper end of the chamber is in fluid communication, via a control line, with a hydraulic fluid source and pump at the surface. Seals are provided such that when sufficient control fluid (e.g. hydraulic fluid) pressure is supplied from surface, the rod piston moves downwardly in the chamber, thus forcing the flow tube downwardly through the flapper to open the valve. When the control fluid pressure is removed, the rod piston and flow tube move upwardly allowing the biasing spring to move the flapper and thus the valve, to the closed position.
On relatively rare occasions, the safety valve assembly may become inoperable or malfunction due to the buildup of materials such as paraffin, fines, and the like on the components downhole, e.g., such that the flapper may not fully close or may not fully open. Regardless, it is known to replace the TRSSSV by retrieving the safety valve assembly to surface by pulling the entire tubing string from the well and replacing the safety valve assembly with a new assembly, and then rerunning the safety valve and the tubing string back into the well.
Because of the length of time and expense required for such a procedure, it is known to run a replacement safety valve downhole within the tubing retrievable safety valve as described hereinafter. These replacement safety valves typically are run downhole via a wireline. Thus, these replacement safety valves are often referred to as wireline retrievable sub-surface safety valves (“WRSSSV”). Before inserting the wireline safety valve into the TRSSSV assembly, however, two operations are performed. First, the TRSSSV is locked in its open position (i.e., the flapper must be maintained in the open position); and second, fluid communication is established from the existing control fluid line to the interior of the TRSSSV, thus providing control fluid (e.g. hydraulic fluid) to the replacement wireline safety valve. Lockout tools perform the former function; communication tools perform the latter.
Various lockout tools are commercially available, and will not be further discussed herein. When it is desired to lock the safety valve assembly in its open position, the lockout tool is lowered through the tubing string and into the safety valve. The lockout tool is then actuated to lock the valve mechanism (e.g. the flapper) of the TRSSSV in the open position.
Before inserting the replacement safety valve or WRSSSV, communication is established between the hydraulic chamber of the TRSSSV and the internal diameter of the TRSSSV. The communication tool disclosed herein may be utilized to provide fluid communication between the inner diameter of the safety valve and the hydraulic chamber, so that the hydraulic control line from surface can be utilized to operate the replacement wireline safety valve.
Once communication has been established with the hydraulic line, the WRSSSV may be run downhole. The WRSSSV may resemble a miniature version of the TRSSSV assembly described above. The WRSSSV is adapted to be run downhole and placed within the inner diameter of the TRSSSV assembly described above. The WRSSSV typically includes an upper and lower set of seals that will straddle the communication flow passageway established by them communication tool so that the control line to the TRSSSV may be used to actuate the valve mechanism of the WRSSSV.
More specifically, the seal assemblies allow control fluid from the control line to communicate with the hydraulic chamber and piston of the WRSSSV in order to actuate the valve of the WRSSSV between the open and closed positions. Once the WRSSSV is in place, the wireline may be removed and the tubing string placed on production.
There are various methods of establishing communication used today. One such method involves inserting a communication tool downhole which must be radially aligned just fight in order for the cutter to cut the required communication point. Some of these tools require special sleeves which precisely position the communication tool in exact alignment.
There are disadvantages to these designs. If the alignment is off, the cutter will miss the intended communication point and communication will not be established. This may also lead to costly damage to the interior of the tool. Also, designing and installing the sleeves used to align the tools is costly and may introduce unnecessary leak paths in the tubing.
In view of the foregoing, there is a need in the art for, among others, a cost effective communication tool which establishes fluid communication without the need for alignment of the tool or the costly components associated therewith.